Issue background

Reflected cross-site scripting vulnerabilities arise when data is copied from a request and echoed into the application's immediate response in an unsafe way. An attacker can use the vulnerability to construct a request which, if issued by another application user, will cause JavaScript code supplied by the attacker to execute within the user's browser in the context of that user's session with the application.

The attacker-supplied code can perform a wide variety of actions, such as stealing the victim's session token or login credentials, performing arbitrary actions on the victim's behalf, and logging their keystrokes.

Users can be induced to issue the attacker's crafted request in various ways. For example, the attacker can send a victim a link containing a malicious URL in an email or instant message. They can submit the link to popular web sites that allow content authoring, for example in blog comments. And they can create an innocuous looking web site which causes anyone viewing it to make arbitrary cross-domain requests to the vulnerable application (using either the GET or the POST method).

The security impact of cross-site scripting vulnerabilities is dependent upon the nature of the vulnerable application, the kinds of data and functionality which it contains, and the other applications which belong to the same domain and organisation. If the application is used only to display non-sensitive public content, with no authentication or access control functionality, then a cross-site scripting flaw may be considered low risk. However, if the same application resides on a domain which can access cookies for other more security-critical applications, then the vulnerability could be used to attack those other applications, and so may be considered high risk. Similarly, if the organisation which owns the application is a likely target for phishing attacks, then the vulnerability could be leveraged to lend credibility to such attacks, by injecting Trojan functionality into the vulnerable application, and exploiting users' trust in the organisation in order to capture credentials for other applications which it owns. In many kinds of application, such as those providing online banking functionality, cross-site scripting should always be considered high risk.

Issue remediation

In most situations where user-controllable data is copied into application responses, cross-site scripting attacks can be prevented using two layers of defenses:

Input should be validated as strictly as possible on arrival, given the kind of content which it is expected to contain. For example, personal names should consist of alphabetical and a small range of typographical characters, and be relatively short; a year of birth should consist of exactly four numerals; email addresses should match a well-defined regular expression. Input which fails the validation should be rejected, not sanitised.

User input should be HTML-encoded at any point where it is copied into application responses. All HTML metacharacters, including < > " ' and =, should be replaced with the corresponding HTML entities (&lt; &gt; etc).

In cases where the application's functionality allows users to author content using a restricted subset of HTML tags and attributes (for example, blog comments which allow limited formatting and linking), it is necessary to parse the supplied HTML to validate that it does not use any dangerous syntax; this is a non-trivial task.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/api/

Issue detail

The value of the data request parameter is copied into the HTML document as plain text between tags. The payload daaba<img%20src%3da%20onerror%3dalert(1)>d9c1376791d2c3b4a was submitted in the data parameter. This input was echoed as daaba<img src=a onerror=alert(1)>d9c1376791d2c3b4a in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.

The original request used the POST method, however it was possible to convert the request to use the GET method, to enable easier demonstration and delivery of the attack.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/api/

Issue detail

The value of the data request parameter is copied into the HTML document as plain text between tags. The payload 546a9<img%20src%3da%20onerror%3dalert(1)>68378bef2a6 was submitted in the data parameter. This input was echoed as 546a9<img src=a onerror=alert(1)>68378bef2a6 in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/api/

Issue detail

The value of the format request parameter is copied into the HTML document as plain text between tags. The payload aa996<img%20src%3da%20onerror%3dalert(1)>ba49b2dbe3e209c77 was submitted in the format parameter. This input was echoed as aa996<img src=a onerror=alert(1)>ba49b2dbe3e209c77 in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.

The original request used the POST method, however it was possible to convert the request to use the GET method, to enable easier demonstration and delivery of the attack.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/api/

Issue detail

The value of the ids request parameter is copied into the HTML document as plain text between tags. The payload c8242<img%20src%3da%20onerror%3dalert(1)>ef9354c1c7a53146d was submitted in the ids parameter. This input was echoed as c8242<img src=a onerror=alert(1)>ef9354c1c7a53146d in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.

The original request used the POST method, however it was possible to convert the request to use the GET method, to enable easier demonstration and delivery of the attack.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/api/

Issue detail

The value of the method request parameter is copied into the HTML document as plain text between tags. The payload 7a49a<img%20src%3da%20onerror%3dalert(1)>eab47c7d5b9 was submitted in the method parameter. This input was echoed as 7a49a<img src=a onerror=alert(1)>eab47c7d5b9 in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/api/

Issue detail

The value of the method request parameter is copied into the HTML document as plain text between tags. The payload dc272<img%20src%3da%20onerror%3dalert(1)>29f44677fa745c343 was submitted in the method parameter. This input was echoed as dc272<img src=a onerror=alert(1)>29f44677fa745c343 in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.

The original request used the POST method, however it was possible to convert the request to use the GET method, to enable easier demonstration and delivery of the attack.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/register.html

Issue detail

The value of the city request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload f017a"style%3d"x%3aexpression(alert(1))"a0f8014dbfd was submitted in the city parameter. This input was echoed as f017a"style="x:expression(alert(1))"a0f8014dbfd in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses a dynamically evaluated expression with a style attribute to introduce arbirary JavaScript into the document. Note that this technique is specific to Internet Explorer, and may not work on other browsers.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/register.html

Issue detail

The value of the country request parameter is copied into a JavaScript string which is encapsulated in double quotation marks. The payload 15336"%3balert(1)//3ba577de2ef was submitted in the country parameter. This input was echoed as 15336";alert(1)//3ba577de2ef in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response.

Remediation detail

Echoing user-controllable data within a script context is inherently dangerous and can make XSS attacks difficult to prevent. If at all possible, the application should avoid echoing user data within this context.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/register.html

Issue detail

The value of the firstName request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload %006846a"style%3d"x%3aexpression(alert(1))"28a35c45c82 was submitted in the firstName parameter. This input was echoed as 6846a"style="x:expression(alert(1))"28a35c45c82 in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses a dynamically evaluated expression with a style attribute to introduce arbirary JavaScript into the document. Note that this technique is specific to Internet Explorer, and may not work on other browsers.

The application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by submitting a URL-encoded NULL byte (%00) anywhere before the characters that are being blocked.

Remediation detail

NULL byte bypasses typically arise when the application is being defended by a web application firewall (WAF) that is written in native code, where strings are terminated by a NULL byte. You should fix the actual vulnerability within the application code, and if appropriate ask your WAF vendor to provide a fix for the NULL byte bypass.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/register.html

Issue detail

The value of the lastName request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 836e6"style%3d"x%3aexpression(alert(1))"1316b661e82 was submitted in the lastName parameter. This input was echoed as 836e6"style="x:expression(alert(1))"1316b661e82 in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response. The PoC attack demonstrated uses a dynamically evaluated expression with a style attribute to introduce arbirary JavaScript into the document. Note that this technique is specific to Internet Explorer, and may not work on other browsers.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/register.html

Issue detail

The value of the password request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 78edf"><script>alert(1)</script>c4de70aa9ec was submitted in the password parameter. This input was echoed unmodified in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response.

Summary

Severity:

High

Confidence:

Certain

Host:

http://www.tagged.com

Path:

/register.html

Issue detail

The value of the zipCode request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload c5ad3"><script>alert(1)</script>9c9cbd70a76 was submitted in the zipCode parameter. This input was echoed unmodified in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response.

Issue background

Passwords submitted over an unencrypted connection are vulnerable to capture by an attacker who is suitably positioned on the network. This includes any malicious party located on the user's own network, within their ISP, within the ISP used by the application, and within the application's hosting infrastructure. Even if switched networks are employed at some of these locations, techniques exist to circumvent this defense and monitor the traffic passing through switches.

Issue remediation

The application should use transport-level encryption (SSL or TLS) to protect all sensitive communications passing between the client and the server. Communications that should be protected include the login mechanism and related functionality, and any functions where sensitive data can be accessed or privileged actions can be performed. These areas of the application should employ their own session handling mechanism, and the session tokens used should never be transmitted over unencrypted communications. If HTTP cookies are used for transmitting session tokens, then the secure flag should be set to prevent transmission over clear-text HTTP.

Issue background

Sensitive information within URLs may be logged in various locations, including the user's browser, the web server, and any forward or reverse proxy servers between the two endpoints. URLs may also be displayed on-screen, bookmarked or emailed around by users. They may be disclosed to third parties via the Referer header when any off-site links are followed. Placing session tokens into the URL increases the risk that they will be captured by an attacker.

Issue remediation

The application should use an alternative mechanism for transmitting session tokens, such as HTTP cookies or hidden fields in forms that are submitted using the POST method.

Summary

Issue detail

The page contains a form with the following action URL, which is submitted using the GET method:

http://www.tagged.com/account_info.html

The form contains the following password fields:

password_old

password_new

password_conf

Issue background

The application uses the GET method to submit passwords, which are transmitted within the query string of the requested URL. Sensitive information within URLs may be logged in various locations, including the user's browser, the web server, and any forward or reverse proxy servers between the two endpoints. URLs may also be displayed on-screen, bookmarked or emailed around by users. They may be disclosed to third parties via the Referer header when any off-site links are followed. Placing passords into the URL increases the risk that they will be captured by an attacker.

Issue remediation

All forms submitting passwords should use the POST method. To achieve this, you should specify the method attribute of the FORM tag as method="POST". It may also be necessary to modify the corresponding server-side form handler to ensure that submitted passwords are properly retrieved from the message body, rather than the URL.

Summary

Issue detail

The form contains the following password fields with autocomplete enabled:

password_old

password_new

password_conf

Issue background

Most browsers have a facility to remember user credentials that are entered into HTML forms. This function can be configured by the user and also by applications which employ user credentials. If the function is enabled, then credentials entered by the user are stored on their local computer and retrieved by the browser on future visits to the same application.

The stored credentials can be captured by an attacker who gains access to the computer, either locally or through some remote compromise. Further, methods have existed whereby a malicious web site can retrieve the stored credentials for other applications, by exploiting browser vulnerabilities or through application-level cross-domain attacks.

Issue remediation

To prevent browsers from storing credentials entered into HTML forms, you should include the attribute autocomplete="off" within the FORM tag (to protect all form fields) or within the relevant INPUT tags (to protect specific individual fields).

Issue background

A cookie's domain attribute determines which domains can access the cookie. Browsers will automatically submit the cookie in requests to in-scope domains, and those domains will also be able to access the cookie via JavaScript. If a cookie is scoped to a parent domain, then that cookie will be accessible by the parent domain and also by any other subdomains of the parent domain. If the cookie contains sensitive data (such as a session token) then this data may be accessible by less trusted or less secure applications residing at those domains, leading to a security compromise.

Issue remediation

By default, cookies are scoped to the issuing domain and all subdomains. If you remove the explicit domain attribute from your Set-cookie directive, then the cookie will have this default scope, which is safe and appropriate in most situations. If you particularly need a cookie to be accessible by a parent domain, then you should thoroughly review the security of the applications residing on that domain and its subdomains, and confirm that you are willing to trust the people and systems which support those applications.

Issue background

When a web browser makes a request for a resource, it typically adds an HTTP header, called the "Referer" header, indicating the URL of the resource from which the request originated. This occurs in numerous situations, for example when a web page loads an image or script, or when a user clicks on a link or submits a form.

If the resource being requested resides on a different domain, then the Referer header is still generally included in the cross-domain request. If the originating URL contains any sensitive information within its query string, such as a session token, then this information will be transmitted to the other domain. If the other domain is not fully trusted by the application, then this may lead to a security compromise.

You should review the contents of the information being transmitted to other domains, and also determine whether those domains are fully trusted by the originating application.

Today's browsers may withhold the Referer header in some situations (for example, when loading a non-HTTPS resource from a page that was loaded over HTTPS, or when a Refresh directive is issued), but this behaviour should not be relied upon to protect the originating URL from disclosure.

Note also that if users can author content within the application then an attacker may be able to inject links referring to a domain they control in order to capture data from URLs used within the application.

Issue remediation

The application should never transmit any sensitive information within the URL query string. In addition to being leaked in the Referer header, such information may be logged in various locations and may be visible on-screen to untrusted parties.

Issue background

When an application includes a script from an external domain, this script is executed by the browser within the security context of the invoking application. The script can therefore do anything that the application's own scripts can do, such as accessing application data and performing actions within the context of the current user.

If you include a script from an external domain, then you are trusting that domain with the data and functionality of your application, and you are trusting the domain's own security to prevent an attacker from modifying the script to perform malicious actions within your application.

Issue remediation

Scripts should not be included from untrusted domains. If you have a requirement which a third-party script appears to fulfil, then you should ideally copy the contents of that script onto your own domain and include it from there. If that is not possible (e.g. for licensing reasons) then you should consider reimplementing the script's functionality within your own code.

Issue background

If the HttpOnly attribute is set on a cookie, then the cookie's value cannot be read or set by client-side JavaScript. This measure can prevent certain client-side attacks, such as cross-site scripting, from trivially capturing the cookie's value via an injected script.

Issue remediation

There is usually no good reason not to set the HttpOnly flag on all cookies. Unless you specifically require legitimate client-side scripts within your application to read or set a cookie's value, you should set the HttpOnly flag by including this attribute within the relevant Set-cookie directive.

You should be aware that the restrictions imposed by the HttpOnly flag can potentially be circumvented in some circumstances, and that numerous other serious attacks can be delivered by client-side script injection, aside from simple cookie stealing.

Issue background

The presence of email addresses within application responses does not necessarily constitute a security vulnerability. Email addresses may appear intentionally within contact information, and many applications (such as web mail) include arbitrary third-party email addresses within their core content.

However, email addresses of developers and other individuals (whether appearing on-screen or hidden within page source) may disclose information that is useful to an attacker; for example, they may represent usernames that can be used at the application's login, and they may be used in social engineering attacks against the organisation's personnel. Unnecessary or excessive disclosure of email addresses may also lead to an increase in the volume of spam email received.

Issue remediation

You should review the email addresses being disclosed by the application, and consider removing any that are unnecessary, or replacing personal addresses with anonymous mailbox addresses (such as helpdesk@example.com).

Issue background

If a web response specifies an incorrect content type, then browsers may process the response in unexpected ways. If the specified content type is a renderable text-based format, then the browser will usually attempt to parse and render the response in that format. If the specified type is an image format, then the browser will usually detect the anomaly and will analyse the actual content and attempt to determine its MIME type. Either case can lead to unexpected results, and if the content contains any user-controllable data may lead to cross-site scripting or other client-side vulnerabilities.

In most cases, the presence of an incorrect content type statement does not constitute a security flaw, particularly if the response contains static content. You should review the contents of the response and the context in which it appears to determine whether any vulnerability exists.

Issue remediation

For every response containing a message body, the application should include a single Content-type header which correctly and unambiguously states the MIME type of the content in the response body.